Synthetic drying oils



Patented June 19, 1945 SYNTHETIC DRYING OILS,

Theodore F. Bradley, Stamford, Conn., assignor to American CyanamidCompany, New York, N. Y., a corporation ofMaine No Drawing. ApplicationOctober 4, 1941, Serial No. 413,646

6 Claims. (01. zen-410.6)

This invention relates to a new class of drying oils of improved dryingcharacteristics and to their preparation. More particularly, it relatesto improved drying oils resulting from the esteriflcation of polyallylalcohols containing at least esterifiable primary hydroxyl groups withfatty acids and mixtures thereof containing a relatively high percentageof unsaturated fatty acids and having an iodine value of at least 100.

The naturally occurring drying oils most commonly employed in the artsheretofore, particuother words the common idea has been to estimate theworth of an oil for varnish and paint purposes in terms of the amount ofits unsaturation per unit of weight.

I have found that the iodine value of anoil is a misleading measure ofits drying qualities larly in the manufacture of paints and varnishes,

have consisted essentially of a mixture of triglycerides of higher fattyacids the larger proportion of which are unsaturated. The dryingcharacteristics as well as the heat-bodying or varnish-making qualitiesof these oils have generally been considered to depend primarily uponthe degree and nature of their unsaturation.

The degree ofunsaturation is dependent upon the ratio of linoleic,linolenic, eleostearic or other of the polyenic acid radicals of theglycerides to the oleic and the saturated acid radicals present in theoil and is commonly determined by halogen absorption measurements suchas the iodine value. The nature of the unsaturation is also importantinasmuch as conjugated unsaturation normally leads to appreciably-fasterdrying and to faster heat-bodying oils than does non-con- J'ugatedunsaturation. I have taken advantage of this fact in my isomerizationprocessv disclosed and claimed in my copending application Serial 'No.378,060, filed February 8, 1941, whereby unconjugated double bonds offatty acids are caused to enter into conjugation.

It has generally been considered that the iodine value of a drying oilis the best criterion of its drying qualities and most textbookstherefore classify oils as non-drying, semi-drying and drying inaccordance with their iodine values. A recognized exception is the caseof oils in which the unsaturation is of the conjugated rather than''unconjugated form. Because halogens tend to react incompletely withconjugated'double bonds the ordinary methods of analysis yield iodinevalues which are abnormally low and erroneous because they no longerprovide a true measure of the degree of unsaturation. Hydrogen can bemade to fully saturate conjugated double bonds and the degree ofunsaturation of the .con-

iugated oils has been accurately measured by a determination of theamount of hydrogen required to saturate these oils. To provide a uniformbasis of measurement and a uniform standard these hydrogen values aregenera1ly calculated in terms of their iodine equivalent. Thesehydrogen-iodine values" are therefore analogous to ordinary iodinevalues and both measure the unsaturation of the oils in terms of thepercentage of iodine absorbed per unit weight of an oil. In

since it is actually the amount and kind of unsaturation per molecule ofoil rather than the unsaturation per unit weight that determines dryingspeed and heat gelation. This follows from the general theories ofpolymerization described by me in Industrial 8; Engineering Chemistry,vol. 229, pp. 440, 579 (1937) and is a special case of the broaderconcept that the number of functional groups of each molecule determinesthe gelation and drying characteristics of the oil.

In accordance with the present invention I compensate for the lack of anadequate amount of unsaturation in the majority of the drying oils, notby the customary'means of trying to increase the amount of unsaturationper unit of weight, i. e. the iodine value, but by increasing the numberof double bonds per molecule of the oil. The

present invention accomplishes these, theoretical and practicalobjectives, and others as will appear hereinafter, by the synthesis ofesters in which at least 5 fatty acid radicals have been combined withone molecule of a polyallyl alcohol having at least five es'terifiableprimary hydroxyl groups. According to the principles of this inventionthe larger the number of the combined fatty acid radicals, the fasterthe rate of drying or of heat-gelation and the smaller may be the ratioof polyunsaturated acid radicals to the oleic or saturated acid radicalsof the oil without inhibition of the drying or gelation characteristics.Therefore, I am able to utilize the mixed fatty acids of very poordrying oils such as cottonseed, corn and soya bean oils and convertthese into esters which dry better than ordinary linseed oil withoutwasting or rejecting any of their constituent fatty acids.

I have found that oils produced by esterifying unsaturated higher fattyacids with polyallyl alcohols containing at least five and preferablyconsiderably more than five primary hydroxyl groups possess improveddrying properties as compared with glyceride oils prepared from the samehigher fatty acids.

The polyallyl alcohols employed by me in the preparation of my improveddrying oils may be prepared by blowing a, stream of oxygen throughheated allyl alcohol in a suitable vessel. 3080 cous reaction productwas freed of monomeric allyl alcohol by heating under reduced pressure.

1445 parts by weight of a clear, pale yellow, allyl molecule dependingupon the condition of the polymerization reaction.

Fatty acids employed by me to provide drying oils of improvedcharacteristics include those fatty acids derived from drying andsemi-drying oils as well as the higher unsaturated fatty acids in moreor less pure state. Since the iodine value of fatty acids is a measure'of their degree of unsaturation per unit of weight and the molecularweights of the oil acids are closely equivalent it has been found thatit can be conveniently em ployed to demarcate those fatty acids andfatty acid mixtures which may be reacted with the polyallyl alcohols ofthis invention to yield drying oils of improved properties. AccordinglyI have found that those fatty acids and mixtures thereof having aniodine value 'of at least 100 may be employed in practicing my inventionhereindescribed.

Although it is possible to employ the straight unsaturated fatty acids,for example linoleic acid which has an iodine value of about 181, Iprefer-to use the fatty acids ordinarily commercially obtainable in theform of mixtures of fatty acids obtained by the hydrolysis of animal andvegetable oils. When using fatty acid mixtures obtained from semi-dryingoils, such as cottonseed oil, sunflower seed oil, corn oil, sesame oil,etc., which fatty acid mixtures have iodine values of over 100, withpolyallyl alcohols having at least 5 esterifiable primary hydroxygroups, the oil thus obtained has greatly superior drying propertieswhen compared with its corresponding fatty acid triglyceride. Thisimprovement, I believe, is due to the increased number of double bondsper molecule, i. e. the increased functionality of the new polyallylalcohol esters in comparison with the glycerol ester which has but threeester linkages thus limiting the number of unsaturated functional groupsobtainable in the molecule. These improved drying oils may be employedas such or may be blended with linseed oil, oiticica oil, tung oil, etc.to good advantage.

When I react polyallyl alcohols having at least 5 esterifiable primaryhydroxyl groups with fatty acids derived from drying oils such aslinseed oil, soya bean oil, oiticica oil, perilla oil, dehydrated castoroil, and the like, which have hydrogeniodine values of 130 or more, theproducts possess greatly superior drying properties as compared to thecorresponding glycerol-fatty acid esters. These improved oils show manyof the characteristics of tung oil in time of drying, hardness' of thefilm and water-resistance and may be used in place thereof for manypurposes, Data showing more specifically the drying characteristics ofsuch improved oils are given in theex.- amples and tables which follow.

When preparing my improved drying oils I ordinarily employ substantiallystoichiometrical proportions of the fatty acids and the polyallylalcohols, that is, one molecule of fatty acid is added to the reactionmixture for each esterifiable primary hydroxyl group in the polyallylalcohoi employed. I do not intend to restrict my invention, however, tothe use of substantially stoichiometrical quantities since it may bedesirable in some cases to employ larger quantities of the alcohol oracid constituent.

The reaction whereby the drying oils of the present invention areproduced takes place at elevated temperatures within the range -250 C.and preferably between -215 C. The time required for completing thereaction varies considerably and depends upon the particular reactantsemployed, the temperature, the catalysts (if any), the viscosity of theproduct desired, etc. Accordingly it is most convenient to measure thecourse of the reaction by the acid number of the reaction mixture whichmay be reduced to about 10 or even less when employing stoichiometricquantities of fatty acid and alcohol. However, because of possibleexcessive polymerization of the oil during the heating period Ifrequently stop the reaction when the reaction mixture has been reducedto an acid number of about 20. When an excess of fatty acid has beenemployed these values do nothold and allowance must be made for theexcess of acid. When it is desired to obtain an oil of particularly lowviscosity characteristics I react the mixture under milder conditionsand stop the heating 'at acid values of the order of 35.

In some cases, and particularly when easily polymerizable higher fattyacids are employed such as those derived from linseed oil, soya bean oilor oiticica oil, or where isomerized fatty acids having a high contentof conjugated double bonds are used such as the isomerized acids of soyabean oil, linseed oil and dehydrated castor oil, some difficulty may beexperienced in obtaining an oil having a low hydroxyl value. When thisdifficulty is encountered it can be overcome by adding relatively smallamounts of a reactive monocarboxylic acid of relatively low molecularweight or its anhydride, near the end of the heating period, in order toesterify any hydroxyl groups of the polyhydroxyl alcohol that may nothave been esterified by the higher fatty acid. Thus, for example, inpreparing synthetic drying oils consisting of esters of higherunsaturated fatty acids with polyallyl alcohol having at least 5esterifiable primary hydroxyl groups, stoichidmetric quantities of thefatty acid and alcohol may be heated together in the manner previouslydescribed until a product. having a hydroxyl number of 20-50 isobtained, whereupon the calculated amount or an excess of a lower fattyacid or its anhydride such as acetic acid, propionic acid, butyric acid,acetic anhydride, ketene or other monocarboxylic acid of relatively lowmolecular weight such as benzoic acid, abietic acid, rosin orhydrogenated rosin is added. The heating is then continued, withdistillation of excess lower fatty acid if necessary, until the oil hasa suitably low hydroxyl value.

During the reaction period and while the product is at elevatedtemperatures it is advisable to keep it under an inert atmosphere suchas CO: or

N2 to avoid oxygen induced polymerization. Catalysts such as p-toluenesulfonic acid, zinc chloride, HCl, litharge etc. in amounts of about .1%to 1% may be employed to speed up the reaction if desired but I havefound that their use is not ordinarily necessary.

Upon completion of the esterification the reaction mlxture usuallycontains small percentages of unreacted fatty acids, alcohol and onlypartially esterified alcohols which may be removed to reduce the acidnumber and improve inlet tube leading to the bottom of the reaction thedrying properties 01' th 11, Th t mixture. The mixture was heated on anoil rials may be readily removed by washing the bath and the temperaturebrought t0 Q C- n product with ethyl alcohol as described in the onehour- The Water formFd was dlstmed out examples which follow. It is alsopossible to re- 5 through an outlet tube pmvlded the purpose move theexcess fatty acids by blowing steam a good stream of was mPmtained-dur'mg all of the heating. After heating for 6 hours through the 011,preferably under partlally rea at 200-210 C. the heating was stoppedandthe duced pressure, in the manner of a steam disb t k th t th productcooled and washed three times by extflla'tion but care Should e en i 10traction with ethyl alcohol. The final traces of l heating P causeexcess ve p0 f alcohol were removed by blowing CO1 through mation of the011. Still another method is to d1sthe on at 120430. C till'ofl theundesired constituents under a vacu- Y um of a few millimeters pressure.The alcohol EXAMPLE '2 extraction method is most useful in those casesAn oil was prepared from 180 parts by weight where a very low viscosityoil, as for paints, is to f lyan 1 alcohol and 560 parts b Wei ht of beproduced and the reaction has been stopped 9 y y g f t d f tt isomerizedlinseed fatty acids in the manner dewhne substantial quantifies 0 m? yscribed above. The isomerized linseed fatty acids f Q Rolyhydmxyalcohols remam' In contained 36.8% of fatty acids having two doublehlgher .5 products such as used in bonds in conjugation and 4.6% offatty acids havnishes an alcohol extractmn or other means of mg threedouble bonds in conjugation reducing the acid value below 10 is notusually some of the more important. chemical and necessary. I physicalcharacteristics of the oils prepared in' My ew drying 0115 y be used 111the Same Examples 1 and 2 are given in the following table. manner andfor the same pu poses as drying O s The properties of tung oil, oiticicaoil, and deheretofore used in the art such as in the manuhydrated castoroil are also included for purfacture of paints, varnishes, enamels andother poses of comparison. Viscosity values are given coatingcompositions, alkyd resins, linoleum, on the Gardner-Holdt scale andcolor is indiprinting inks, and many other products. The cated on theVarnish Color System of the Inexamples which follow illustrate in adegree some 311 stitute of Paint and Varnish Research.

Table 1 Visoos Acid Ester s 31 OH Color ity No. value 138. Fwll value YZ-hr.)

Linseed fatty acids!- 'r A 5.2 183:6 188.8 174. 12.7 ggfi;1 i'g a335ijj111 B 8.0 168.2 176.2 162.? 15.5 lsmbmwdhnmdmty acids+ 1 F 5.0 185.4191.4 137.5 14.5 s z 6.1 172.8 178.9 122.0 e2 10 J 7.7 184.0 192.6 164.211 'r 7.1 135.7 192.8 161.4 4 o 8.3 1886 191.9 143.7 25.3

of these uses as well as the preparation of many different types ofesters but are intended to be illustrative rather than in limitation ofmy invention which is to be construed as broadly as the appended claimspermit. .All parts given are by weight.

EXAMPLE 1 The above described drying oils were thinned to practicallythe same viscosity with mineral spirits and then there was added 0.02%cobalt and 0.16% lead as drier. Tin and glass panels were cleaned withtoluene and the various oils applied. The panels were then inclined atapproximately the sanie angle and the oil allowed to dry in a room at aconstant temperature of 24 C. and relative humidity of Throughout thesetests and'in the preparation of the oils it was attempted tomaintain'uniform conditions so that the drying qualities of the oilscould be compared directly.

Table 2 Tin panels Glass panels on Order of Order of s Tackrelative BetTackrelative 2" free, hardness free, ese

' hrs. after 24 hrs. alter 24 hours hours 4.5 5.5 o 3 5.5 7 3.5 4.5 e 35.5 4 a5 a5 2 3 3 1 5.5 5.5 4 3 s 1 a5 4.5- -s 3 a e It will be notedfrom the above that my drying oils compare favorably with tung oil andin most cases are superior to oiticica oil and dehydrated. castor oil indrying time and hardness and show distinct improvement over the resultsobtained with similar oils prepared with glycerol as the alcohol.

These same oils were also tested for heat gelation time and waterresistance of their films. The heat gelation test was made by'a modifiedA. S. -T. M. procedure and consisted in determining the time in minutesnecessary for 5 cc. of the oil to gel in a. 6 inch test tube at atemperature of 282 0., i2 C. In the water resistance test a tin panelcarrying a film of oil dried for at least 48 hours was immersed in waterat 28 C. and examined at periods of 24 hours and 72 hours. The degree ofwhitening of the films was noted. In the table 1 represents nowhitening; 2, very slight trace; 3, trace; 4, considerable; 5, severe;and 6, very severe. The panels were then removed from the water, exposedto the air, and their relative order of recovery noted. The results ofthese tests are as follows:

in my new oils over the corresponding fatty acid triglycerides andfurther show the closeness with which they approach the gelling time andfilm forming properties oftung oil.

EXAMPLE 3 193 parts by weight of polyallyl alcohol and 600 parts byweight of soya bean fatty acids were mixed and heated in a suitablereaction vessel at 200-210 C. until the acid number had dropped to 32.8.The product was then washed 4 .times with ethyl alcohol whereupon theacid number was reduced to 4.5. The viscosity of the oil was reducedwith acetone and it was then filtered through a paint strainer to removea small amount of jelled particles which had formed. Alcohol and acetonewere then removed by blowing with CO2.

EXAMPLE 4 parts by weight of polyallyl alcohol and 282 parts by weightof cottonseed fatty acids were heated at approximately 200 C. Thereaction mixture was stirred and a stream of CO: blown through itthroughout the heating period. The acid number had been reduced to 35.8.The product'was cooled and washed 4 times with ethyl alcohol whereby theacid number was reduced to 5.4. The viscosity of the oil was reducedwith acetone and the material filtered through a paint strainer asabove. then removed by blowing with a stream of CO2.

What I claim is:

l. A method of preparing drying oils with improved drying propertieswhich comprises esterifying a. polyallyl alcohol having at least 5esterifiable primary OH groups with fatty acids having an iodine valueof at least derived from an oil of the group consisting of dehydratedcastor oil, soya beanoil, linseed oil and their conjugated isomers untilat least 5 of the esteriflable primary OH groups have-been esterified.

2. A method of preparing drying oils of improved drying properties whichcomprises esterie fying substantially completely a. polyallyl alco holhaving'att least 5 esterifiable primary OH groups with linseed oil fattyacids.

-3. A method of preparing drying oils of improved drying propertieswhich comprises esterifying substantially completely a polyallyl alcoholhaving at least 5 esterifiable primary OH groups with isomerized linseedoil fatty acids.

4. A method of preparing drying oils-of improved drying properties whichcomprises esteri- 'fying substantially completely a polyallyl alcoholhaving at least 5 esterifiable primary OH groups with dehydrated castoroil fatty acids.

5. A drying oil consisting of a polyallyl alcohol having at least fiveesterifiable primary hydroxy groups esterified with higher fatty acidshaving an iodine value of at least 100, said oil having better dryingcharacteristics than a triglyceride of the same fatty acids. K

6. A method of producing drying oils of improved. drying propertieswhich comprises esterifying a pOlyallyl alcohol having at least fiveesterifiable primary hydroxy groups with higher fatty acids having aniodine value of at least 100 until at least five of the esterifiableprimary hydroxy groups of the alcohol have been esterified.

THEODORE F. BRADLEY.

The alcohol and acetone were

